Electrophotographic compositions and elements

ABSTRACT

CERTAIN 5-BENZYLIDENERHODANINES ARE USEFUL AS PHOTOCONDUCTORS.

United States Patent O US. Cl. 96-1 PC 6 Claims ABSTRACT OF THE DISCLOSURE Certain S-benzylidenerhodanines are useful as photoconductors.

This invention relates to electrophotography and more particularly to a novel class of photoconductive materials and compositions and elements produced therefrom.

Electrophotographic processes employ an electrophotographic or photoconductive element comprising a coating of a photoconductive insulating material on a conductive support. The element is given a uniform surface charge in the dark and then is exposed to an image pattern of activating electromagnetic radiation such as light or X- rays. The charge on the photoconductive element is dissipated in the illuminated area to form an electrostatic charge pattern which is then developed by contact with an electroscopic marking material. The marking material or toner, as it is also called, Whether carried in an insulating liquid or in the form of a dry powder, deposits on the exposed surface in accordance with either the charge pattern or the discharge pattern, as desired. Then, if the photoconductive element is of the non-reusable type, the developed image is fixed by fusion or other means to the surface of the photoconductive element. If the element is of the reusable type, e.g., a selenium-coated drum, the image is transferred to another surface such as paper and then fixed to provide a copy of the original.

All of this is well-known and has been described in many patents and other literature, for example, in the patent of Carlson, U.S. 2,297,691, and in more recent works such as Electrophotography by R. M. Schafiert, published by Focal Press Ltd., 1965.

The photoconductive compounds that have been used in electrophotographic processes have included both organic and inorganic compounds. The organic photoconductors have been desirable for a number of reasons. For instance, the organics are less abrasive than the inorganics. They can be charged to high negative or positive potential While the inorganics often saturate at low potential and accept only a positive or a negative charge. In addition, the organics usually otter greater exposure latitude, can be spectrally sensitized more effectively and offer a number of other advantages over zinc oxide and other inorganics.

However, the selection of photoconductive compounds for incorporation into electrophotographic compositions has proceeded on a compound-by-compound basis. Nothing as yet has been discovered from the large number of different photoconductive substances tested which permits efiective prediction and, therefore, selection of which compounds will exhibit desirable electrophotographic properties.

It is, therefore, an object of this invention to provide a novel class of photoconductive compounds.

3,719,489 Patented Mar. 6, 1973 It is another object of this invention to provide a novel class of photoconductors having high photosensitivity when electrically charged.

It is still another object of this invention to provide novel transparent electrophotographic elements having useful electrophotographic speeds.

It is a further object of this invention to provide an improved process utilizing the novel photoconductors described herein.

These and other objects and advantages are accomplished in accordance with this invention by the use of S-benzylidenerhodanines as organic photoconductors in electrophotographic imaging systems. The rhodanines disclosed herein may be used alone, if desired, but their utility is greatly enhanced by their use in conjunction with photosensitizing addenda as set forth in greater detail hereinafter.

The S-benzylidenerhodanines which are useful in the preparation of electrophotographic elements according to this invention are those corresponding to the general formula:

wherein R is an aryl radical selected from the group consisting of a carbazolyl radical, a julolidyl radical and an amino substituted aryl radical including a substituted aminosubstituted aryl radical;

R is hydrogen, an alkyl radical or an aryl radical;

R is hydrogen, an alkyl radical, an aryl radical including a substituted aryl radical or a benzylideneamino radical;

W is an oxygen atom or a sulfur atom;

X is an oxygen atom or a sulfur atom;

Z is an oxygen atom, a sulfur atom or an arylimino radical; and

n is O or 1.

Exemplary of the radicals which can be represented by R are monovalent radicals such as the following:

R has the same meaning as set forth above;

R has the same meaning as set forth above;

R and R may be hydrogen, an alkyl radical, an aryl radical or an aralkyl radical and may be the same or difierent;

m may have either of the values set forth for n, and may be the same as n or different;

W, X and Z may be any of those substituents set forth for W, X and Z, respectively; and

which may be substituted with a radical such as a lower alkyl radical or a lower alkoxy radical.

Preferred photoconductors according to the invention are those corresponding to the formula:

R and R; may be a lower alkyl radical or an aryl radical including a substituted aryl radical, and may be the same or different;

R is hydrogen or a lower alkyl radical;

R is hydrogen, a lower alkyl radical, an aryl radical including a substituted aryl radical, or a benzylideneamino radical;

R is a lower alkyl radical, a lower alkoxy radical or hydrogen;

R and R when taken separately, are hydrogen atoms and when taken together represent the number of carbon atoms necessary to complete a phenylene, naphthylene or anthrylene nucleus; and

W, X, Z and n have the same meanings set forth hereinbefore.

Particularly preferred photoconductors according to the invention are those corresponding to the formula:

wherein:

R and R may be a lower alkyl radical or a phenyl radical including a substituted phenyl radical hearing as substituents a lower alkyl radical or a halogen atom;

R is hydrogen, a lower alkyl radical, a phenyl radical including a phenyl radical substituted with a lower alkylamino group or lower dialkylamino group, or is a benzylideneamino radical including an amino substituted benzylideneamino radical;

R is hydrogen, a lower alkyl radical or a lower alkoxy radical;

W is an oxygen atom or a sulfur atom; and

Z" is a sulfur atom or a phenylimino radical.

The term alkyl radica as used herein refers to an alkyl radical having from 1 to about 8 carbon atoms, e. g., methyl, ethyl, isopropyl, cert-butyl, hexyl, octyl, etc., including a substituted alkyl radical having from 1 to about 8 carbon atoms in the alkyl moiety such as (a) aminoalkyl, e.g., aminobutyl, aminoethyl, aminopropyl, etc.,

(b) aralkyl, e.g., benzyl, phenethyl, etc.,

() alkylaminoalkyl, e.g., ethylaminopropyl, methylaminoethyl, etc., and also including dialkylaminoalkyl, e.g., diethylaminoethyl, dimethylaminopropyl, propylaminooctyl, etc.,

(d) arylaminoalkyl, e.g., phenylaminoethyl, and also including diarylaminoalkyl, e.g., diphenylaminomethyl, =N-phenyl-N-ethylaminopentyl, dinaphthylaminopropyl, etc.,

(e) cyanoalkyl, e.g., cyanopropyl, cyanobutyl, etc.,

(2) haloalkyl, e.g., chloromethyl, bromopentyl, chlorooctyl, etc.

The term lower alkyl radical as used herein refers to an al-kyl radical having from 1 to about 4 carbon atoms, e.g., methyl, ethyl, isopropyl, butyl, etc.

The term lower alkoxy radical as used herein refers to an alkoxy radical having from 1 to about 4 carbon atoms in the alkyl moiety, e.g., methoxy, ethoxy, propoxy, butoxy, etc.

The term aryl radica as used herein refers to a monoor polycyclic, carbocyclic aromatic radical, e.g., phenyl, anthryl, naphthyl, etc., and including corresponding substituted aryl radicals such as (a) aminoaryl, e.g., aminophenyl, aminonaphthyl, aminoanthryl, etc.,

(b) alkylaminoaryl, e.g., ethylaminophenyl, methylaminonaphthyl, etc., and also including dialkylaminoaryl, e.g., diethylaminophenyl, dipropylaminonaphthyl, etc.,

(0) arylaminoaryl, e.g., phenylaminophenyl, and also including diarylaminoaryl, e.g., diphenylaminophenyl, -N- phenyl N-ethylaminophenyl, dinaphthylaminophenyl, etc.,

(d) alkaryl, e.g., tolyl, ethylphenyl, propylnaphthyl, etc.,

(e) cyanoaryl, e.g., cyanophenyl, cyanonaphthyl, etc.,

(f) haloaryl, e.g., chlorophenyl, bromonaphthyl, etc.

The term benzylideneamino radica as used herein refers to a radical having the formula: -N=CHAr' where Ar represents a phenyl radical including substituted phenyl radicals.

The term arylimino radical as used herein refers to a radical having the formula: =N- wherein Ar" represents an aryl radical such as phenyl, naphthyl, etc., as well as substituted aryl radicals. Preferred arylimino radicals are phenylimino radicals.

Exemplary photoconductors useful for preparing the photoconductive compositions and elements of the invention include the following:

( l 5- (p-dimethylaminobenzylidene -3-n-propylrhodanine (2) 5- (p-dimethylaminocinnamylidene)-3-ethylrhodanine (3 5 p-diethylaminobenzylidene -3-phenylrhodanine (4) 5- (p-diphenylaminobenzylidene -3-ethylrhodanine (5 5- [p-(di-p-tolylarnino) benzylidene] -3-ethylrhodanine (6) 5-(p-dimethylaminobenzylidene)-3-phe11y1-2-pheny1- imino-4-thiazolidinone 7 5 (p-diphenylaminoben zylidene) -3-phenyl-2-phenylimino-4-thiazolidinone 8) 5- [p-(di-p'-tolylamino)benzylidene] -3-phenyl-2- phenylimino-4-thiazolidinone (9) 5- (p-diphenylaminobermylidene) -3-(p-dimethylamin0- phenyl) rhodanine l0) 5- (4'-diphenylaminol-naphthylidene) -3-ethyl- (1 l) S-(pdiphenylaminoo-methoXybenzylidene)-3-ethylrhodanine rhodanine (12) S-[p- (di-p'-bromophenylamino)benzylidene1-3- ethylrhodanine l3 3-ethyl-S-benzylidenerhodanine 14) 5- (p-diphenylaminobenzylidene) rhodanine (1'5) S-(p-diphenylaminobenzylidene)-3-ethyl-2-thioxo 4- oxazolidinone 16) 5- (diphenylaminobenzylidene rhodanine-N-acetic acid (17) 5-[p-(N-methyl-N-phenylamino)benzylidene] -3- ethylrhodanine (18) 5-(p-diphenylamino-o-methylbenzylidene)-'3-ethylrhodanine l9) 5- (p-diphenylaminobenzylidene -3- (p-diphenylaminobenzylideneimino rhodanine (20) 3-ethyl-5-(9-ethylcarbazol-3'-yl)rhodanine (21 5- (9'-julolidinyl) -3-ethylrhodanine (22) p,p-bis[i( 3-ethyl-4-0x0-2-thioico-5-thiazolidinylidene)methyl] N-methyldi henyl amine According to this invention, it has been found that the photoconductors described herein yield compositions and elements which have enhanced electrophotographic properties when compared to those photoconductors described in the prior art. These enhanced properties are observed when the elements accept a suitable surface potential (e. g., 500600 volts) and are subsequently exposed to actinic radiation. The relative electrophotographic speed of the element is determined on the basis of the reciprocal of the exposure required to reduce the potential of the surface charge by 100 volts (shoulder speed) or to 100 volts (toe speed. The terms shoulder speed and toe speed are terms known in the photographic art with reference to H and D curves. As used herein, such terms refer to corresponding curves resulting from exposure plotted against voltage. The reduction of the surface potential to 100 volts or below is significant in that it represents a requirement for suitable broad area development of an electrostatic image. The relative speed at 100 volts is a measure of the ability to produce and hence to develop or otherwise utilize the electrostatic image. When many conventional photoconductors are used, the surface potential frequently does not drop to or below 100 volts and, therefore, no toe speed can be assigned to such a composition. The photoconductive compositions disclosed herein do exhibit useful toe speeds.

The photoconductive compounds used in preparing the photoconductive compositions and elements of this invention are prepared generally by condensing the appropriate aldehyde with a rhodanine compound. Compound 3 is made, for example, by condensing p diethylaminobenzaldehyde with 3-phenylrhodanine in the presence of ;8- alanine. If the aldehyde is not available, it is first synthesized, as with Compounds 5, 8, 11 and 12, for example. Compound 2 is prepared as described by M. Strell and S. Reindl, Arch. Pharm., 293, 984-91 (1960), while the preparation of Compound 14 is given in German Pat. 1,041,048. Compound 1 is sold by Eastman Organic Chemicals, a division of Eastman Kodak Company (No. 9985).

Electrotrophotographic elements of the invention can be prepared with the photoconducting compounds of the invention in the usual manner, i.e., by blending a dispersion or solution of a photoconductive compound together with a binder, when necessary or desirable, and coating or forming a self-supporting layer with the photoconductor-containing materials. Mixtures of the photoconductors described herein can be employed. Likewise, other photoconductors known in the art such as those described in Light British Pat. 1,153,506, dated May 29, 1969, can be combined with the present photoconductors. In addition, supplemental materials useful for changing the spectral sensitivity or electrophotosensitivity of the element can be added to the composition of the element when it is desirable to produce the characteristic efiect of such materials.

Preferred binders for use in preparing the present photoconductive layers are film-forming, polymeric binders having fairly high dielectric strength which are good electrical ly insulating film-forming vehicles. Materials of this type comprise styrene-butadiene copolymers; silicone resins; styrene-alkyd resins; silicone-alkyd resins; soya-alkyd resins; poly(vinyl chloride); poly(viny1idene chloride); vinylidene chloride acrylonitrile copolymers; poly(vinyl acetate); vinyl acetate-vinyl chloride copolymers; poly- (vinyl acetals), such as poly(vinyl butyral); polyacrylic and methacrylic esters, such as poly(methyl methacrylate), poly(n-butyl methacrylate), poly(isobutyl methacrylate), etc.; polystyrene; nitrated polystyrene; poly (methyl styrene); isobutylene polymers; polyesters, such as copoly[ethylene co alkylenebis(alkyleneoxyaryl)phenylenedicarboxylate] e. g., poly [ethylene-co-isopropylidene-2, 2-bis(ethyleneoxyphenyl)terephthalate]; phenolformaldehyde resins; ketone resins; polyamides; polycarbonates; polythiocarbonates; copolymers of vinyl haloarylates and vinyl acetate such as poly(vinyl-m-bromobenzoate-covinyl acetate); waxes and chlorinated polyethylene.

Solvents useful for preparing coating compositions with the photoconductors of the present invention can include a wide variety of organic solvents for the components of the coating composition. For example, benzene; toluene; acetone; 2-butanone; chlorinated hydrocarbons such as methylene chloride, ethylene chloride and the like; ethers, such as tetrahydrofuran and the like, or mixtures of such solvents can advantageously be employed in the practice of this invention.

In preparing the coating compositions, useful results are obtained where the photoconductor substance is present in an amount equal to at least about 1 Weight percent of the coating composition. The upper limit in the amount of photoconductor substance present can be widely varied in accordance with the usual practice. In those cases where a binder is employed, it is normally required that the photoconductor substance be present in an amount from about 1 weight percent of the coating composition to about 99 Weight percent of the coating composition. A preferred weight range for the photoconductor substance in the coating composition is from about 10 weight percent to about 60 weight percent.

Sensitizing compounds useful with the photoconductive elements of the present invention can be selected from a wide variety of materials, including such materials as pyrylium dye salts including thiapyryliurn dye salts and selenapyrylium dye salts disclosed in VanAllen et al. U.S. Pat. 3,250,615; fluorenes, such as 7,12-dioxo-13-dibenzo- (a,h)fluorene, 5,10 dioxo-4a,l1-diazabenzo(b)fluorene, 3, 13-dioxo-7-oxadibenzo(b,g)fiuorene, and the like; aggregate-type sensitizers of the type described in Belgian Pat. 705,117, dated Apr. 16, 1968; aromatic nitro compounds of the kind described in U.S. Pat. 2,610,120; anthrones like those disclosed in U.S. Pat. 2,670,284; quinones, U.S. Pat. 2,670,286; benzophenones, U.S. Pat. 2,670,287; thiazoles, U.S. :Pat. 2,732,301; mineral acids; carboxylic acids, such as maleic acid, diand trichloroacetic acids, and salicyclic acid; sulfonic and phosphoric acids; and other electron acceptor compounds as disclosed by H. Hoegl, J. Phys. Chem, 69, No. 3, 755-766 (March 1965), and U.S. Pat. 3,232,755.

The amount of sensitizer that can be added to a photoconductor layer to give effective increases in speed can vary widely. The optimum concentration will vary with the specific photoconductor and sensitizing compound used. In general, substantial speed gains can be obtained Where an appropriate sensitizer is added in a concentration range from about 0.0001 to about 10 Weight percent or more based on the weight of the coating composition. Normally, sensitizers are added to the coating composition in an amount of about 0.005 to about 5.0 percent by weight of the total coating composition.

Although no sensitizer is required to produce a photoconductive response in the compositions of this invention, sensitizers are desirable because a relatively minor amount of sensitizer can give substantial improvements in speed or sensitivity.

Coating thicknesses of the photoconductive composition on a support can vary widely. Normally, a wet coating thickness in the range of about 25 microns to about 250 microns is useful in the practice of the invention. A preferred range of coating thickness is from about 50 microns to about microns'before drying although such thicknesses can vary widely depending on the particular application desired for the electrophotographic element.

Suitable supporting materials for the photoconductive layers of the present invention can include any of the electrically conducting supports, for example, various conducting papers; aluminum-paper laminates; metal foils, such as aluminum foil, Zinc foil, etc.; metal plates such as aluminum, copper, zinc, brass, and galvanized plates; vapor deposited metal layers such as silver, nickel or aluminum on conventional film supports such as cellulose acetate, poly(ethylene terephthalate), polystyrene and the like conducting supports. An especially useful conducting support can be prepared by coating a transparent film support material such as poly(ethylene terephthalate) with a layer containing a semiconductor dispersed in a resin. Also, a suitable conducting coating can be prepared from the sodium salt of a carboxy-ester lactone of a maleic anhydride-vinyl acetate copolymer, cuprous iodide and the like. Such conducting layers and methods for their optimum preparation and use are disclosed in Minsk U.S. Pat. 3,007,901, dated Nov. 7, 1961, Trevoy U.S. Pat. 3,245,833, dated Apr. 12, 1966, and Sterman et a1. U.S. Pat. 3,262,- 807, dated July 26, 1966.

The compositions of the present invention can be employed in photoconductive elements useful in any of the well known electrophotographic processes which require photoconductive layers. One such process is the Xero graphic process. In a process of this type, an electrophotographic element held in the dark, is given a blanket positive or negative electrostatic charge as desired by placing it under a corona discharge to give a uniform charge to the surface of the photoconductive layer. This charge is retained by the layer owing to the substantial dark insulating property of the layer, i.e., the low conductivity of the layer in the dark. The electrostatic charge formed on the surface of the photoconductive layer is then selectively dissipated from the surface of the layer by imagewise exposure to light by means of a conventional exposure operation such as, for example, by a contact-printing technique, or by lens projection of an image, or reflex or bireflex techniques and the like, to thereby form a latent electrostatic image in the photoconductive layer. Exposing the surface in this manner forms a pattern of electrostatic charge by virtue of the fact that light energy striking the photoconductor causes the electrostatic charge in the light struck areas to be conducted away from the surface in proportion to the illuminance on a particular area.

The charge pattern produced by exposure is then developed or transferred to another surface and developed there, i.e., either the charged or uncharged areas rendered visible, by treatment with a medium comprising electrostatically responsive particles having optical density. The developing electrostatically responsive particles can be in the form of a dust, or powder and generally comprise a pigment in a resinous carrier called a toner. A preferred method of applying such a toner to an electrostatic image for solid area development is by the use of a magnetic brush. Methods of forming and using a magnetic brush toner applicator are known in the art, e.g., Young U.S. Pat. 2,786,439, Giaimo U.S. Pat. 2,786,440, and Young U.S. Pat. 2,786,441, all dated Mar. 26, 1957. Liquid development of the latent electrostatic image may also be used. In liquid development, the developing particles are carried to the image-bearing surface in an electrically insulating liquid carrier. Methods of development of this type are widely known and have been described in the patent literature, for example, Metcalfe et a1. U.S. Pat. 2,907,674, dated Oct. 6, 1959. In dry developing processes, the most widely used method of obtaining a permanent record is achieved by selecting a developing particle which has as one of its components a low-melting resin. Heating the powder image then causes the resin to melt or fuse into or on the element. The powder is, therefore, caused to adhere permanently to the surface of the photoconductive layer. In other cases, a transfer of the charge image or powder image formed on the photoconductive layer can be made to a second support such as paper which would then become the final print after developing and fusing or fusing, respectively. Techniques of the type indicated are well known in the art and have been described in the literature, such as in RCA Review, vol. (1954), pages 469-484.

The compositions of the present invention can be used in electrophotographic elements having many structural variations. For example, the photoconductive composition can be coated in the form of single layers or multiple layers on a suitable opaque or transparent conducting sup port. Likewise, the layers can be contiguous or spaced having layers of insulating material or other photoconductive material between layers or overcoated or interposed between the photoconductive layer or sensitizing layer and the con-ducting layer. It is also possible to adjust the position of the support and the conducting layer by placing a photoconductor layer over a support and coating the exposed face of the support or the exposed or overcoated face of the photoconductor with a conducting layer. Configurations ditfering from those contained in the examples can be useful or even preferred for the same or different application for the electrophotographic element.

The following examples are included for a further understanding of the invention.

EXAMPLE 1 Several compositions in the form of dopes comprised of the following material-s are each coated at a wet thickness of 150 microns on a poly(ethylene terephthalate) film support bearing a conductive layer of vapor deposited nickel:

Photoconductor (see below) 0.25 Binder poly(4,4-isopropylidene-bisphenyleneoxyethylene-co-ethylene terephthalate 1.00 Sensitizer 2,6-bis(4-ethylphenyl)-4-(4-n-amyloxyphenyl)thiapyrylium perchlorate 0.01

Dichloromethane 9.60

The support is held on a coating block maintained at a temperature of about 32 C. during coating and until the solvent is removed. In a darkened room, the surface of the photoconductive layer of each of the resultant electrophotographic elements is charged to a potential of about }+600 volts under a corona charger. The layer is then covered with a transparent sheet bearing a pattern of opaque and light-transmitting areas and exposed to the radiation from an incandescent lamp with an illumination intensity of about 75 meter-candles for 12 seconds. The resulting electrostatic charge pattern is developed by cascading over the surface of the layer negatively charged black thermoplastic toner particles on glass bead carriers. All of the elements produce a visible image, except the one which contains no photoconductor.

EXAMPLE 2 Elements prepared as in Example 1 are each recharged under a positive corona source until the surface potential, as measured by an electrometer probe, reaches about 600 volts. They are then exposed from behind a stepped density gray scale to a 3000 K. source. The exposure causes reduction of the surface potentials of the elements under each step of the gray scale from their initial value, V to some lower potential, V, whose exact value depends on the actual amount of exposure received by the areas. The results of the measurements are plotted on a graph of surface potential, V, vs. log exposure for each step. The speed of each element, as shown in Table I, is the numerical expression of 10 multiplied by the reciprocal of the exposure in meter-candle-seconds required to reduce the 600 volt charged surface potential to volts (toe speed).

9 EXAMPLE 3 The procedure of Example 2 is followed replacing the sensitizer with an equal weight of Rhodamine B (C.I. 45170). The photoconductors tested and the speeds which are obtained are given in Table II below.

The procedure of Example 2 is repeated only the sensitizer is replaced with an equal weight of 2,4,7-trinitrofiuoren-9-one. The results of these tests are given in Table III below.

TABLE III Photoconductor: Toe speed None 1 13 3 12 4 21 7 12 8 17 9 33 10 10 EXAMPLE A first dye-containing solution is prepared by dissolving 0.03 g. of the dye 2,6-diphenyl-4-(4-dimethylaminophenyl)thiapyrylium perchlorate in 7.65 g. of dichloromethane. A second solution containing dye and polymer is prepared by dissolving 3.92 g. of poly(4,4'-isopropylidenediphenylene carbonate) (Lexan 145, General Electric Co.) in 20.0 g. of dichlorornethane which contains 0.08 g. of the above dye in solution. The second solution is subjected to shearing in a high-speed blender for a half-hour at room temperature. The two solutions are then incorporated into a photoconductor-containing coating solution to form a coating dope for each of the photoconductors listed in Table IV below. The photoconductor-containing solution is prepared according to the following com position:

Lexan 145 0.25

Photoconductor 0.25 Solution Each of the coating dopes thus produced is coated as in Example 1 to form photoconductive elements. Each element is then charged positively and exposed as in Example 2 through a stepped density gray scale. The speeds obtained are listed in Table IV.

10 EXAMPLE 6 The procedure of Example 5 is repeated, with the exception that the speed is measured in terms of the exposure required to reduce the 600 volt surface potential by volts (shoulder speed), for the photconductors listed in Table V.

TABLE V Photoconductor: Speed None 750 1 2000 3 3800 4 1900 5 3600 6 3200 7 3200 8 2500 9 2500 10 2300 11 2200 12 1800 14 1000 15 2500 17 3200 18 3200 19 2200 21 1400 EXAMPLE 7.PREPARATION OF COMPOUND 6 An ethanolic solution of p-dimethylaminobenzaldehyde (3.0 g., 0.02 mole), 3-phenyl-2-phenylimino-4-thiazolodinone (5.4 g., 0.02 mole) and 1 ml. of piperidine is heated to reflux and allowed to cool to room temperature for 24 hours. A precipitate results, which is collected and recrystallized from ml. nitromethane. The yield is 2.8 g., and the melting range of the product is 212.5213.0 C. The theoretical values calculated for C H N OS and the values actually found are as follows:

Calculated (percent): C, 71.4; H, 5.5; N, 10.9; S, 8.3. Found (percent): C, 71.8; H, 5.3; N, 10.6; S, 8.2.

EXAMPLE 8.PREPARATION O'F COMPOUND 7 An ethanolic solution of 4-formyltriphenylamine (5.4 g., 0.02 mole), 3-phenyl-2-phenylimino-4-thiazolidinone (5.4 g., 0.02 mole) and 1 ml. of piperidine is heated to reflux and allowed to cool in a refrigerator at 5 C. for 16 hours. The crystalline product is collected and recrystallized from 100 ml. nitromethane. The yield is 1.9 g. of product having a melting range of 221.0-221.5 C. The theoretical values calculated for C H N OS and the values actually found are as follows:

Calculated (percent): C, 78.0; H, 4.7; N, 8.0; S, 6.1. Found (percent): C, 77.6; H, 4.7; N, 8.2; S, 6.2.

EXAMPLE 9.PREPARATION OF COMPOUND 8 (A) 4-di- (p-tolyl aminobenzaldehyde To a rapidly stirred solution of 27.3 g. (0.1 mole) 4,4- dimethyltriphenylamine in 50 ml. of N,N-dimethylformamide is slowly added phosphorous oxychloride (28.0 g., 0.18 mole). 4,4'-dimethyltriphenylamine is made according to Marsden, J. Chem. Soc. 1937, 627. Stirring is continued for 30 minutes at room temperature and for an additional two hours on a steam bath. The product is hydrolyzed by drowning in 1500 ml. of water saturated with sodium acetate. After an hour, the aqueous layer is decanted and the residue dissolved in chloroform. The chloroform solution is washed with water and dried, and the chloroform evaporated under vacuum. The residue is recrystallized from nitromethane to yield 50 grams of product melting at 103 C. The theoretical values calculated for C H NO and the values actually found are as follows:

Calculated (percent): C, 83.7; H, 6.3; N, 4.6. Found (percent): C, 83.5; H, 6.5; N, 4.5.

(B) Preparation of Compound 8 To 150 ml. of boiling ethanol is added 6.0 g. (0.02 mole) of 4-di(p-tolyl)arninobenzaldehyde, 5.4 g. (0.02 mole) of 3-phenyl-2-phenylimino-4-thiazolidinone and 1 ml. of piperidine. The solution is cooled at 5 C. for 16' hours, precipitating crystals which are separated by filtration. The product is recrystallized from 500 ml. nitromethane, to yield 6.8 g. of crystals which melt at 257- 259 C. The theoretical values calculated for C H N OS and the values actually found are as follows:

Calculated (percent): C, 78.3; H, 5.3; N, 7.6; S, 5.8. Found (percent): C, 78.2; H, 5.4; N, 7.4; S, 5.7.

EXAMPLE 10.PREPARATION OF COMPOUND 17 The intermediate, p-(N-methyl-N-phenyl)arninobenzaldehyde, is prepared by the procedure of Vilsmeyer and Hack, Ber., 60B, 119-122 (1926). An ethanolic solution of 2.1 g. (0.01 mole) of this aldehyde, 1.6 g. (0.01 mole) of S-ethylrhodanine, 0.5 ml. of piperidine and 0.5 ml. of acetic acid are heated to reflux and cooled at 5 C. for 24 hours. The product is isolated by filtration and recrystallized from 75 ml. of nitromethane. There results 1.0 g. of crystals which melt in the range of 118-119 C. The theoretical values calculated for C H N OS and the values actually found are as follows:

Calculated (percent): C, 64.3; H, 5.1; N, 7.9; S, 18.1. Found (percent): C, 64.3; H, 5.0; N, 7.8; S, 18.1.

EXAMPLE 11.PREPARATION OF COMPOUND 18 (A) Preparation of m-methyltriphenylamine An 84 g. portion (0.5 mole) of diphenylamine, 120 g. (0.87 mole) of anhydrous potassium carbonate and a catalytic quantity (3 g.) of copper powder are placed in a 2- liter boiling flask. To this is added 500 g. (2.3 moles) of m-iodotoluene. The solution is allowed to reflux with continuous stirring. A Dean-Stark trap is used to remove water generated by the reaction. When the reaction is complete, the excess m-iodotoluene is removed by steam distillation. The product is extracted into benzene and passed through a bed of neutral alumina to remove colored impurities. The solvent is evaporated and the clear residue crystallized from 500 ml. of ethanol to yield 94 g. of product. Recrystallization from 800 ml. of ethanol yields 71 g. of product having a melting range of 65-66 C. The theoretical values calculated for C I-I N and the values actually found are as follows:

Calculated (percent): C, 88.0; H, 6.6; N, 5.4.. Found (percent): C, 87.9;H, 6.8; N, 5.5.

(B) Preparation of p-formyl-m-methyltriphenylamine To 200 ml. of N,N-dimethylformamide at room temperature is added 25.9 g. (0.1 mole) of rn-methyltriphenylamine. When solution is complete, 16.8 g. (0.11 mole) of phosphorous oxychloride is slowly added, with stirring. The solution is then heated on a steam bath for 16 hours and drowned in 1000 ml. of saturated aqueous sodium acetate solution. The water-insoluble fraction is collected, dissolved in chloroform, and the chloroform solution washed with water. After drying with magnesium sulfate, the chloroform is evaporated and the residue extracted into toluene and passed through a short bed of neutral alumina to remove dark colored products. The toluene is evaporated and the residue crystallized from 200 ml. of isopropanol. There results 6.3 g. of product having a melting range of 158l58.5 C. The theoretical values calculated for C H NO and the values actually found are as follows:

Calculated (percent): C, 83.0; H, 6.6; N, 4.8. Found (percent): C, 83.1; H, 6.4; N, 4.8.

(C) Preparation of Compound 18 A solution of 2.9 g. (0.01 mole) of p-formyl-m-methyltriphenylamine, 1.6 g. (0.01 mole) of 3-ethylrhodanine,

0.5 ml. of piperidine and 0.5 ml. of acetic acid is heated to reflux and cooled at 5 C. for 2 hours. A crystalline product separates which is recrystallized from 40 ml. of nitromethane. There results 2.0 g. of crystals having a melting range of l29-130 C. The theoretical values calculated for C H N OS and the values actually found are as follows:

Calculated (percent): C, 69.5; H, 5.1; N, 6.5; S, 14.9. Found (percent): C, 69.4; H, 5.1; N, 6.6; S, 14.8.

EXAMPLE 12.PREPARATION OF COMPOUND 19 A solution of 5.4 g. 4-formyltriphenylamine (0.02 mole), 1.5 g. 3-aminorhodanine (0.01 mole), 0.5 ml. piperidine and 0.5 m1. acetic acid are heated on a steam bath for an hour and allowed to cool to room temperature. After allowing the mixture to stand for several hours at room temperature, the solvent is decanted from a gummy precipitate. The gum is dissolved in toluene, loaded on a short bed of neutral alumina and eluted with ethyl ether. Evaporation of the solvent and crystallization from nitromethane gives 0.8 g. of product having a melting range of 246.0247.0 C. The theoretical values calculated for C H N OS and the values actually found are as follows:

Calculated (percent): C, 74.6; H, 4.6; N, 8.5; S, 9.7. Found (percent): C, 74.6; H, 4.9; N, 8.6; S, 9.4.

EXAMPLE l3.-PREPARATION OF COMPOUND 21 A solution of 3.2 g. (0.02 mole) of 3-ethylrhodanine, 4.0 g. (0.02 mole) of 9-formyljulolidine, 0.5 ml. of piperidine and 0.5 ml. acetic acid in 200 ml. of ethanol is heated to reflux and stored at 5 C. for one week. The product is then isolated and recrystallized twice from nitromethane. There results 4.4 g. of product melting in the range of 218-219 C. The theoretical values calculated for C H N OS and the values actually found are as follows:

Calculated (percent): C, 62.7; H, 5.9; N, 8.1; S, 18.6. Found (percent): C, 62.6; H, 6.0; N, 8.4; S, 19.0.

EXAMPLE l4.PREPARATION OF COMPOUND 22 (A) Preparation of 4,4'-diformyl-N- methyldiphenylamine To a rapidly stirred solution of 200 g. (1.08 mole) of N-methyldiphenylamine in 500 m1. N,N-dimethylformamide is slowly added 350 g. (2.28 moles) phosphorous oxychloride. The reaction vessel is immersed in a water bath held at 15 C. during the addition. When addition is completed, the vessel is heated on a steam bath for four hours and drowned in 2 liters of water containing 0.454 kg. of sodium acetate. The aqueous mixture is stirred and allowed to stand at room temperature for 16 hours. The product is isolated by decanting the aqueous layer and extracting the organic material into chloroform. After washing the chloroform solution with Water and drying over magnesium sulfate, the chloroform is evaporated. Distillation of the residue yields 48.5 g. of p-(N-methyl- N-phenyl)benzaldehyde having a boiling range of C. (1 and 70.5 g. of 4,4'-diformly-N-methyldiphenylamine having a boiling point of C. (1,11). The theoretical values calculated for C H NO and the values actually found are as follows:

Calculated (percent): C, 75.5; H, 5.5; N, 5.9. Found (percent): C, 75.8; H, 5.5; N, 5.8.

(B) Preparation of Compound 22 A solution of 7.2 g. (0.03 mole) of 4,4-diformyl-N- methyldiphenylamine, 10.1 g. (0.03 mole) of 3-ethylrhodanine, 0.5 ml. of acetic acid and 0.5 ml. of piperidine in 13 300 ml. of methanol is refluxed for four hours and allowed to stand overnight at room temperature. The product separates and is recrystallized twice from nitromethane to yield 4.3 g. of crystals melting from 228.5229.5 C. The theoretical values calculated for C H N O S and the values actually found are as follows:

Calculated (percent): C, 57.0; H, 4.4; N, 8.0. Found (percent): C, 56.6; H, 4.4; N, 7.9.

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

I claim:

1. In an electrophotographic process comprising the steps of electrostatically charging the surface of an electrophotographic element and imagewise exposing said element to a pattern of actinic radiation to selectively reduce the surface charge in accordance with the radiation pattern, the improvement wherein said element comprises an electrically conductive support having thereon a layer of a photoconductive composition comprising an electrically insulating, film-forming polymeric binder having dispersed therein at least about 1% by weight of a photoconductive compound having the formula:

wherein:

R is an aryl radical selected from the group consisting of a carbazolyl radical, a julolidyl radical and an amino-substituted aryl radical;

R is selected from the group consisting of a hydrogen atom, an alkyl radical and an aryl radical;

R is selected from the group consisting of a hydrogen atom, an alkyl radical, an aryl radical and a benzylideneamino radical;

W and X are each selected from the group consisting of an oxygen atom and a sulfur atom;

Z is selected from the group consisting of an oxygen atom, a sulfur atom and an arylimino radical; and

n is O or 1.

2. An electrophotographic process as described in claim 1 wherein R is a monovalent radical selected from the group consisting of:

and

wherein:

R R and R are each selected from the group consisting of hydrogen, an alkyl radical and an aryl radical;

R is selected from the group consisting of hydrogen,

an alkyl radical, an aryl radical and a benzylideneamino radical;

W and X are each selected from the group consisting of an oxygen atom and a sulfur atom;

Z' is selected from the group consisting of an oxygen atom, a sulfur atom and an arylimino radical;

Ar is a divalent carbocyclic aromatic radical containing up to about 14 carbon atoms; and

m is 0 or 1.

3. The process as described in claim 2 wherein said photoconductive composition contains a sensitizing amount of a sensitizer for said photoconductive compound.

4. In an electrophotographic process comprising the steps of electrostatically charging the surface of an electrophotographic element and imagewise exposing said element to a pattern of actinic radiation to selectively reduce the surface charge in accordance with the radiation pattern, the improvement wherein said element comprises an electrically conductive support having thereon a layer of a photoconductive composition comprising an electrically insulating, film-forming polymeric binder having dispersed therein at least about 1% by weight of a photoconductive compound having the formula:

R and R are each selected from the group consisting of a lower alkyl radical and an aryl radical;

R is selected from the group consisting of hydrogen and a lower alkyl radical;

R is selected from the group consisting of hydrogen,

a lower alkyl radical, an aryl radical and a benzylideneamino radical;

R is selected from the group consisting of hydrogen, a lower alkyl radical and a lower alkoxy radical;

R and R 2, when taken separately, are hydrogen atoms, and when taken together, represent the number of carbon atoms necessary to complete a divalent aromatic radical selected from the group consisting of a phenylene radical, a naphthylene radical and an anthrylene radical;

W and X are each selected from the group consisting of an oxygen atom and a sulfur atom;

Z is selected from the group consisting of an oxygen atom, a sulfur atom and an arylimino radical; and

n is 0 or 1.

5. In an electrophotographic process comprising the steps of electrostatically charging the surface of an electrophotographic element and imagewise exposing said element to a pattern of actinic radiation to selectively reduce the surface charge in accordance with the radiation pattern, the improvement wherein said element comprises an electrically conductive support having thereon a layer of a photoconductive composition comprising an electrically insulating, film-forming polymeric binder having dispersed therein at least about 1% by weight of a photoconductive compound having the formula:

R and R are each selected from the group consisting of a lower alkyl radical and a phenyl radical; R is selected from the group consisting of hydrogen, a lower alkyl radical, a benzylideneamino radical and a phenyl radical;

R is selected from the group consisting of hydrogen, a lower alkyl radical and a lower alkoxy radical;

W is an oxygen atom or a sulfur atom; and

Z" is a sulfur atom or a phenylimino radical.

6. In an electrophotographic process comprising the steps of electrostatically charging the surface of an electrophotographic element and imagewise exposing said element to a pattern of actim'c radiation to selectively reduce the surface charge in accordance with the radiation pattern, the improvement wherein said element com- 5-[p-(N-methyl-N-phenylamino) benzylidene1-3- prises an electrically conductive support having thereon ethylrhodanine; a layer of a photoconductive composition comprising an 5- (p-diphenylamino-o-methylbenzylidene)-3- electrically insulating, film-forming polymeric binder havethylrhodanine. ing dispersed therein at least about 1% by weight of a 5 References Cited photoconductive compound selected from the group con- UNITED STATES PATENTS SStmg 3,352,680 11/1967 Taber et a1. 96-84 5-(p-diethylammobenzylidene)-3-phenylrhodanme; 3,246,983 4/1966 Sus et al. 961.5 X 5-[p-( i-p'- lylamino)benzyli n lylr 3 110,591 11 1953 Stewart 95 1.7 5-(p-dimethylaminobenzylidene)-3-phenyl-2-pheny1- 10 imino-4-thiazolidinone; OTHER REFERENCES 5-(p-diphenylaminobenzylidene)-3-phenyl-2-phenylimino-4-thiazolidinone;

5- [pdi-p'-to1ylamino) benzylidene] -3-phenyl-2- phenylimino-4-thiazolidinone;

5- (p-diphenylaminobenzylidene)-3-(p-dimethyl- Kearns, D. R., Electrical Properties of Organic Solids,"

(Thesis) Lawrence Radiation Laboratory, University of 15 California, Berkeley, Calif., Contract No. W-74O 5-eng- 48 (Mar. 25, 1960), pp. L12.

aminophenyDrhodanine; 5- [p-(di-p'-bromophenylamino)benzylidene1-3- CHARLES VAN HORN Pnmary Exammet ethylrhodanine; U.S. Cl. X.R. 5-(p-diphenylaminobenzylidene)-3-ethyl-2-thioxo- 2o 96 1'5 L6;

4-oxazolidinone; 

